A prepreg, an intermediate material commonly used for making a composite material, is usually made of a resin matrix and a reinforcement (such as fibers or fabrics) impregnated in the matrix. The prepreg has higher mechanical strength due to the inclusion of the reinforcement, and is often used to make parts that need to be partially or wholly reinforced, such as motor vehicle components. Commercially available prepregs are often in a sheet or roll form.
The motor vehicle components that need to be reinforced are usually three-dimensional, and sometimes of a complex shape. A known method for making such a three-dimensional component includes the steps of:
Step 1: cutting a purchased prepreg into a suitable shape and dimension (which is obtained by two-dimensionally deploying a desired three-dimensional preform) and stacking a plurality of layers of prepregs of a suitable shape and dimension as required to form a semi-product;
Step 2: heating and then hot stamping the semi-product to form a three-dimensional preform;
Step 3: taking the three-dimensional preform out of a hot stamping die and then mechanically machining (such as contour finishing or drilling) the same after cooling to provide it with a desired final dimension and geometrical configuration;
Step 4: re-heating the three-dimensional preform to a temperature higher than a melting point of a prepreg resin matrix, so as to provide the prepreg resin matrix and an overmolded resin with good adhesion in subsequent overmolding;
Step 5: transferring the hot three-dimensional preform to an overmolding die to overmold a thermoplastic resin portion on the three-dimensional preform by means of injection molding, thereby finally obtaining a three-dimensional component including a reinforcement (composed of the three-dimensional preform) and an overmolded resin portion.
During the processing, a robotic arm is usually used to grab a semi-product or a three-dimensional preform made of a prepreg and then put the same on a retractable needle within a die so as to support and retain the semi-product or the three-dimensional preform made of the prepreg in a position opposite to a forming portion of the die. When it is a long distance for the robotic arm to grab and deliver the semi-product or the three-dimensional preform made of the prepreg, or when the die is still in an open state, such a needle seems to be particularly necessary.
However, there must be a needle control means included in an apparatus in order to control the aforesaid needle, so an additional space is required. Additionally, these tapered needles may leave holes in the semi-product, or leave cones in the three-dimensional preform after injection of thermoplastics. Moreover, when the semi-product or the three-dimensional preform made of the prepreg is heated until the prepreg resin matrix softens, the operation thereof becomes tougher, and the use of the needle alone cannot support and position it well.
In order to support and position the semi-product or the three-dimensional preform made of the prepreg in the processing, in addition to a technical solution using a needle, there is also a known solution using a molding frame, in which a prepreg floating suspension system is adopted. The semi-product or three-dimensional preform, however, may slide between mold cavities during forming, so the system cannot precisely position the semi-product or three-dimensional preform in the die all the time.
Thus, it is required to provide an alternative that can better support and position the semi-product or three-dimensional preform during the processing, in particular, the thermo processing thereof.